Wick lined vanes and their manufacture

ABSTRACT

A vane to be cooled by circulation of a coolant through a metal felt lining in the vane, and its manufacture. The interior of the sheet metal vane wall is provided with bosses which are distributed over the surface and which extend through the metal felt so as to provide a suitable reaction point for dies which are used to form the vane wall and metal felt lining into airfoil form.

United States Patent 2,699,598 [/1955 Daugherty Inventor Jerome V. Lentz Plainfield, Ind.

Appl. No. 879,109

Filed Nov. 24, 1969 Patented Dec. 14, 1971 Assignee General Motors Corporation Detroit, Mich.

WICK LINED VANES AND THEIR MANUFACTURE 1 I Claims, 7 Drawing Figs.

US. Cl 416/96, 415/114, 29/l56.8 Int. Cl Fold 5/08 Field of Search 416/96, 95, 97;4l5/1l4,ll5

References-Cited UNITED STATES PATENTS I III 966 McCormick 4/l967 McCormick OTHER REFERENCES Mechanical Engineering, Feb. 1967, Vol. 89, No. 2, pages 30- 33 Primary Examiner-Everette A. Powell, Jr. Attorneys-Paul Fitzpatrick and Jean L. Carpenter ABSTRACT: A vane to be cooled by circulation of a coolant through a metal felt lining in thevane, and its manufacture. The interior of the sheet metal vane wall is provided with bosses which are distributed over the surface and which extend through the metal felt so as to provide a suitable reaction point for dies which are used to form the vane wall and metal felt lining into airfoil form.

PATENTEU M81419?! .5 1

INVENTUR.

dzrome (Z en/z WICK LINED VANES AND THEIR MANUFACTURE The invention herein described was made in the course of work under a contract or subcontract thereunder with the Depattment of Defense.

My invention is directed to structure of turbine vanes and blades and other similar devices which are cooled by circulation of a coolant which may exist in both liquid and vapor states and which is circulated by means of a wicklike material such as a metal felt which lines the blade. While such cooling systems for high temperature airfoils in turbines have been previously proposed, a difficulty has existed in their manufacture, primarily because of the fact that the vane ordinarily comprises a sheet metal wall with a metal felt lining or inner layer. The inner layer must be applied and bonded to the wall before the wall is formed into the vane and, because of the nature of the metal felt, it is ill-adapted to resist any significant degree of pressure in the forming of the blade or airfoil.

According to my invention, this problem is minimized by modifying the blade wall to provide it with a considerable number of closely spaced bosses extending from the inner surface of the wall through the metal felt so that a reaction point for forces which are used to form the blade is provided, minimizing the exertion of force on the felt. By the nature of the bosses, they have substantially no capability to interfere with the flow of coolant in the metal felt.

The principal objects of my invention are to provide an improved cooled turbine vane or blade and to provide a structure better adapted to forming into blades or vanes of desired contour. A further object is to provide an improved process for the manufacture of metal felt lined airfoils.

The nature of my invention and its advantages will be clear to those skilled in the art from the succeeding detailed description of the preferred embodiment of the invention and the accompanying drawings thereof.

FIG. 1 is an elevation view of a turbine vane or other airfoil.

FIG. 2 is a plan view of the inner surface of the vane wall after formation of bosses thereon. I

FIG. 3 is a sectional view illustrating a further stage in the preparation of a blank.

FIG. 4 is a sectional view illustrating a still further stage in the manufacture of vanes.

FIG. 5 illustrates a step in the forming of the vane.

FIG. 6 illustrates a further step in the forming of the vane.

FIG. 7 is a cross-sectional view of the airfoil showing the closing of the sheet around an internal punch or support.

FIGS. 1 and 7 illustrate an airfoil 10 which specifically as illustrated is intended for use as a nozzle vane of a high temperature turbine. The vane 10 might, for example, be used in a system such as that disclosed in McCormick US. Pat. No. 3,287,906 for Cooled Gas Turbine Vane, Nov. 9, I966. It will be understood that the airfoil I0 might be a part of a turbine blade or might be a part of some other structure, but henceforth in this specification it will be referred to as a vane for conciseness.

The vane is cooled by capillary circulation of a cooling medium which has both liquid and vapor states and which is circulated by capillary action through a feltlike layer of metal lining the inner surface of the airfoil. As shown in FIGS. 1 and 7, the airfoil 10 comprises a metal sheet 11 which preferably is of a high temperature resistant metal commonly used in gas turbines. The metal sheet 11 is formed to define a typical blade having a leading edge 12, a convex face 14, a concave face 15, and a trailing edge 16 at which the two edges of the metal blank from which the blade is formed are brought together. The vane may be twisted so as to have a difierent angular setting at one end of the airfoil from the other. As employed in a turbine nozzle, the vane 10 may have open ends and may be suitably mounted in shroud rings to provide an annular cascade of vanes.

The vane is formed from a blank 18 (FIGS. 3 and 4) comprising a metal sheet 19 having numerous bosses 20 projecting from its inner surface; that is, the surface which is on the inside of the vane after it is formed. The blank also includes a layer 22 of metal felt on the inner surface of the blade. Preferably, in the preferred embodiment, the sheet 19 is of I-Iastelloy X (trademark) and the metal felt layer 22 is of stainless steel. The metal felt is similar to compacted fine metal wool and is available commercially under the name "Feltmetal." It is held to the blade wall by brazing.

Because of the porous nature of the metal felt, it is illadapted to resist heavy loads during forming of the vane. To take care of this difficulty, the bosses 20 are provided. These bosses, which extend from the inner surface of the sheet 19, might be small pieces of metal brazed or welded to the sheet. However, I prefer to provide 'the bosses by chemically milling a sheet to eat away the metal between the bosses. This may readily be done by providing a photoresist to cover the bosses 20 and then etching the material to the desired depth between the bosses. Preferably, the pattern of bosses is similar to that illustrated in FIG. 2 in that the bosses are elongated spanwise of the airfoil and narrow chordwisel It is also believed desirable to put the bosses in echelon asindicated so that the distribution of bosses is relatively uniform spanwise of the airfoil. The relatively narrow bosses provide no significant resistance to forming of the airfoil which is primarily by bending about spanwise extending lines.

The metal felt layer 22, which is in the form of a sheet, is machined by electric discharge machining or otherwise to provide holes in the felt sheet such that the sheet can be fitted over the bosses 20. The metal sheet and felt layer are then prepared for furnace brazing, assembled together, and brazed to fix the felt layer to the metal sheet.

Preferably, the thickness of the metal felt layer 22 varies over the inner surface of the vane. To achieve this variation in thickness and also. to reduce the height of bosses 20 to the thickness of the felt, the felt and bosses are milled to provide a desired cross section. Milling is preferably accomplished by electrochemical milling. The stock or blank 18 is now ready for the forming into the vane.

The technique of forming may be similar to those used on plain sheet metal stock to form them into airfoils or, more generally, the techniques used in forming curved metal surfaces from sheet metal stock. There is a difference in this case, however, in that very high unit pressures cannot be exerted against the metal felt without compressing it and impairing its character. For this reason a punch is used or padded with rubber of 65 durometer hardness to distribute the punch force over the material.

FIGS. 5 and 6 generally illustrate steps of the forming process. In FIG. 5, the blank 18 which has been slightly folded at the leading edge 12 is being pressed into a female die 23 having a cavity 24 corresponding generally to the concave face 14 of the airfoil Force is being exerted by a bar 24 through a rubber sheet 26. In FIG. 6, the concave surface 15 of the blade is being formed on the convex surface 27 of a male die 28. Here a punch 30 having a two blunt edges 31 is working the blank 18 against the die by repeated blows exerted against the pad 26. When the curved surfaces have been formed, the folding at the leading edge is completed and the trailing edge may be welded or brazed if desired. The folding is accomplished to size the vane by pressing against the outer surfaces while the interior of the vane is supported by a properly formed punch 32. In this step, the bosses 20 are forced against punch 32 and act to protect the felt layer 22.

Thereafter hot creep dies may be used to set the twist and thus complete the contours of the vane to a relatively high degree of accuracy.

It is believed that it will be clear to those skilled in the art from the foregoing that I have provided a highly suitable method for providing a heat pipe type cooled vane or other airfoil.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting or restricting the invention, as many modifications may be made by the exercise of skill in the art.

I claim:

l. A method of manufacture of a hollow airfoil having a continuous capillary felt lining comprising: providing a sheet of metal with bosses distributed over and projecting from the sheet; providing a sheetlike body of capillary metal felt material; cutting holes in the body to receive the said bosses; bonding the felt material to the sheet to provided a capillary metal felt layer on the sheet with the summits of the bosses conforming to the exposed surface of the layer, thus providing a blade blank; and forming the blade blank into an airfoil configuration by application of force to the blank.

2. A method of manufacture of a hollow airfoil having a continuous capillary felt lining comprising: providing a sheet of metal with bosses distributed over and projecting from the sheet; providing a sheetlike body of capillary metal felt material; cutting holes in the body to receive the said bosses; mounting the felt material on the sheet to provide a capillary metal felt layer on the sheet; bonding the layer to the sheet; machining the layer and the summits of the bosses to a desired contour of varying thickness with the summits of the bosses conforming to the exposed surface of the layer, thus providing a blade blank; and forming the blade blank into an airfoil configuration by application of force to the surfaces of the blank.

3. A method of manufacture of a hollow airfoil having a continuous capillary felt lining comprising: providing a sheet of metal; machining one face of the sheet to provide a blank of reduced general thickness with bosses distributed over and projecting from the sheet; providing a sheetlike body of capillary metal felt material; cutting holes in the body to receive the said bosses; bonding the felt material to the sheet to provide a capillary metal felt layer on the sheet with the summits of the bosses conforming to the exposed surface of the layer, thus providing a blade blank; and forming the blade blank into an airfoil configuration by application of force to the blank.

4. A method of manufacture of a hollow airfoil having a continuous capillary felt lining comprising: providing a sheet of metal; machining one face of the sheet to provide a blank of reduced general thickness with bosses distributed over and projecting from the sheet; providing a sheetlike body of capillary metal felt material; cutting holes in the body to receive the said bosses; mounting the felt material on the sheet to provide a capillary metal felt layer on the sheet; bonding the layer to the sheet; machining the layer and the summits of the bosses to a desired contour of varying thickness with the summits of the bosses conforming to the exposed surface of the layer, thus providing a blade blank; and forming the blade blank into an airfoil configuration by application of force to the blank.

5. A method as recited in claim 4 in which the bosses are elongated in the direction spanwise of the airfoil and narrow in the direction chordwise of the airfoil.

6. A method as recited in claim 5 in which the bosses are disposed in echelon.

7. A hollow airfoil having a capillary metal felt lining for cooling of the airfoil, the airfoil comprising a sheet metal facing defining the outer surface of the airfoil, the facing having bosses extending from and distributed over its inner surface, the bosses being elongated spanwise of the airfoil relative to the dimension chordwise of the airfoil, and a layer of capillary metal felt bonded to the inner surface of the facing and extending between the said bosses.

8. A hollow airfoil having a capillary metal felt lining for cooling of the airfoil, the airfoil comprising a sheet metal facing defining the outer surface of the airfoil, the facing having bosses extending from and distributed over its inner surface, the bosses being elongated spanwise of the airfoil relative to the dimension chordwise of the airfoil, and a layer of capillary metal felt of varying thickness bonded to the inner surface of the facing and extending between the said bosses, the bosses having their exposed surfaces conforming substantially to the surface of the metal felt layer.

9. A hollow formed tubular member having a capillary metal felt lining for cooling of the member, the member com prising a sheet metal facing defining the outer surface of the member, the facing having bosses extendin from and distnbuted over its inner su ace, the bosses erng elongated lengthwise of the member relative to the transverse dimension, and a layer of capillary metal felt bonded to the inner surface of the member and extending between the said bosses.

10. A blank for forming into a hollow tubular member having curved surfaces and having a capillary felt lining, the blank comprising a sheet of metal having distributed bosses projecting from one face of the sheet and a capillary metal felt layer fitting between and around the bosses and bonded to the sheet, the height of the bosses being substantially equal to the thickness of the layer so that the bosses serve to protect the metal felt against excessive compressive forces during forming of the blank, and capillary flow paths through the metal felt are continuous through spaces between the bosses.

11. A blank as recited in claim 10 in which the thickness of the metal felt layer and height of the bosses varies over the surface of the blank.

* I t i i 

1. A method of manufacture of a hollow airfoil having a continuous capillary felt lining comprising: providing a sheet of metal with bosses distributed over and projecting from the sheet; providing a sheetlike body of capillary metal felt material; cutting holes in the body to receive the said bosses; bonding the felt material to the sheet to provided a capillary metal felt layer on the sheet with the summits of the bosses conforming to the exposed surface of the layer, thus providing a blade blank; and forming the blade blank into an airfoil configuration by application of force to the blank.
 2. A method of manufacture of a hollow airfoil having a continuous capillary felt lining comprising: providing a sheet of metal with bosses distributed over and projecting from the sheet; providing a sheetlike body of capillary metal felt material; cutting holes in the body to receive the said bosses; mounting the felt material on the sheet to provide a capillary metal felt layer on the sheet; bonding the layer to the sheet; machining the layer and the summits of the bosses to a desired contour of varying thickness with the summits of the bosses conforming to the exposed surface of the layer, thus providing a blade blank; and forming the blade blank into an airfoil configuration by application of force to the surfaces of the blank.
 3. A method of manufacture of a hollow airfoil having a continuous capillary felt lining comprising: providing a sheet of metal; machining one face of the sheet to provide a blank of reduced general thickness with bosses distributed over and projecting from the sheet; providing a sheetlike body of capillary metal felt material; cutting holes in the body to receive the said bosses; bonding the felt material to the sheet to provide a capillary metal felt layer on the sheet with the summits of the bosses conforming to the exposed surface of the layer, thus providing a blade blank; and forming the blade blank into an airfoil configuration by application of force to the blank.
 4. A method of manufacture of a hollow airfoil having a continuous capillary felt lining comprising: providing a sheet of metal; machining one face of the sheet to provide a blank of reduced general thickness with bosses distributed over and projecting from the sheet; providing a sheetlike body of capillary metal felt material; cutting holes in the body to receive the said bosses; mounting the felt material on the sheet to provide a capillary metal felt layer on the sheet; bonding the layer to the sheet; machining the layer and the summits of the bosses to a Desired contour of varying thickness with the summits of the bosses conforming to the exposed surface of the layer, thus providing a blade blank; and forming the blade blank into an airfoil configuration by application of force to the blank.
 5. A method as recited in claim 4 in which the bosses are elongated in the direction spanwise of the airfoil and narrow in the direction chordwise of the airfoil.
 6. A method as recited in claim 5 in which the bosses are disposed in echelon.
 7. A hollow airfoil having a capillary metal felt lining for cooling of the airfoil, the airfoil comprising a sheet metal facing defining the outer surface of the airfoil, the facing having bosses extending from and distributed over its inner surface, the bosses being elongated spanwise of the airfoil relative to the dimension chordwise of the airfoil, and a layer of capillary metal felt bonded to the inner surface of the facing and extending between the said bosses.
 8. A hollow airfoil having a capillary metal felt lining for cooling of the airfoil, the airfoil comprising a sheet metal facing defining the outer surface of the airfoil, the facing having bosses extending from and distributed over its inner surface, the bosses being elongated spanwise of the airfoil relative to the dimension chordwise of the airfoil, and a layer of capillary metal felt of varying thickness bonded to the inner surface of the facing and extending between the said bosses, the bosses having their exposed surfaces conforming substantially to the surface of the metal felt layer.
 9. A hollow formed tubular member having a capillary metal felt lining for cooling of the member, the member comprising a sheet metal facing defining the outer surface of the member, the facing having bosses extending from and distributed over its inner surface, the bosses being elongated lengthwise of the member relative to the transverse dimension, and a layer of capillary metal felt bonded to the inner surface of the member and extending between the said bosses.
 10. A blank for forming into a hollow tubular member having curved surfaces and having a capillary felt lining, the blank comprising a sheet of metal having distributed bosses projecting from one face of the sheet and a capillary metal felt layer fitting between and around the bosses and bonded to the sheet, the height of the bosses being substantially equal to the thickness of the layer so that the bosses serve to protect the metal felt against excessive compressive forces during forming of the blank, and capillary flow paths through the metal felt are continuous through spaces between the bosses.
 11. A blank as recited in claim 10 in which the thickness of the metal felt layer and height of the bosses varies over the surface of the blank. 